This paper aims to design and simulate the surface-micromachining micro tunable capacitor for parameters optimization. This work also creates an equivalent circuit model of micro tunable capacitor and proceeds relative electromechanical analysis, including the distribution of field and charge, resonant frequency and pull-in voltage analysis. This micro tunable capacitor is constructed by one suspended top metal plate and two stationary bottom metal plates (one is signal electrode and the other one is bias electrode). By driving electrostatic force, the gap between top and bottom electrodes will be changed and results in a variation of capacitance. To increase the tuning range, the micro tunable capacitor with two different gap space will be presented in this research. High frequency analysis, equivalent circuit analysis and electromechanical dynamic analysis are using Ansoft HFSS, Agilent ADS and the IntelliSuite software respectively. Through these simulation and analysis, it is possible to obtain the optimized specification of micro tunable capacitor. The quality factor (Q) and the pull-in voltage extracted by simulation software well match to the measured results; thus, the function of the analysis method and equivalent model adopted in this thesis can be demonstrated.

The development of magnetic technologies employing microfabricated magnetic structures for the production of integrated electronic components is a driving topic in the electronic industry. Despite the large amount of work reported in the literature towards the production of magnetic devices that can be integrated into conventional silicon technology, the published research has only achieved moderate success. The research presented in this thesis was conducted with the aim to progress towards the production of a magnetic MEMS relay based on electro-deposited NiFe that combines magnetic and electrostatic actuation and that can be integrated in a standard IC processing chain. This work includes a comprehensive design study for the proposed MEMS device and presents the development of the manufacturing processes required for its fabrication. As the theoretical performance of the device is found to be crucially reliant on the mechanical and magnetic properties of the microformed structures, a series of novel test methodologies has been devised and implemented with the aim of acquiring knowledge on the behaviour of the NiFe films. Novel mechanical test routines employing microfabricated test structures are presented and applied to build a systematic and robust system for the characterisation of the electrodeposited films. The quantitative mapping of residual stress at the wafer level using microfabricated test structures has been demonstrated for the first time and applied to optimise processes and tools. A complete fabrication process flow for manufacturing the designed magnetic MEMS switch has been proposed and the fabrication of the actuated section of the switch has been demonstrated, comprising all the functional electric and magnetic components. The fabricated magnetic devices have been tested to monitor their response to an external magnetic force and prove their viability for use in MEMS actuators. Additional work was finally conducted towards the development of a reliable and robust process aimed at increasing the device yield and thus facilitating the eventual commercialisation of magnetic MEMS switches.

In order to apply to S-Band (1-4.5 GHz) of wireless communication system, we designed and fabricated a high-insolating RF-MEMS switch by surface micromachining technology in this study. In terms of the micro switch, we performed the structural design, high frequency simulation, components process integration and high-frequency measurement in this study. Especially for making components be high-isolation, low-loss and low-driving voltage, we proposed the following three methods: (i) adjusting the space and width of the transmission lines to improve the RF performance; (ii) applying the stress imbalance, by using dual metal composite top electrode, to form a arched contact electrode and reduce the drive voltage efficiently; (iii) using non-isometric spring structure to stabilize the electrode movement of the components. Besides, we did the optimizing simulation for this study, which were supported by Ansoft-HFSS and ADS, in terms of the micro switch which has different structural design as mentioned above. The size of the optimized RF micro-switch which we developed for this study is only 145 £gm ¡Ñ 205 £gm. Switched from on-state to off-state, the component needs 36.5V drive voltage only. According to the result of the commercial network analyzer in 1-4.5GHz frequency range, the isolation rate of the components reaches -59.721dB while off-state; the insert los reaches -1.625dB while on-state.

A reflective type Fresnel lens using an array of micromirrors is designed and fabricated using the MUMPs?? surface micromachining process. The focal length of the lens can be rapidly changed by controlling both the rotation and translation of electrostatically actuated micromirrors. The suspension spring, pedestal and electrodes are located under the mirror to maximize the optical efficiency. The micromirror translation and rotation are plotted versus the applied voltage. Relations are provided for the fill-factor and the numerical aperture as functions of the lens diameter, the mirror size, and the tolerances specified by the MUMPs?? design rules. Linnik interferometry is used to measure the translation, rotation, and flatness of a fabricated micromirror. The reflective type Fresnel lens is controlled by independent DC voltages of 16 channels with a 0 to 50V range, and translational and torsional stiffness are calibrated with measured data. The spot diameter of the point source by the fabricated and electrostatically controlled reflective type Fresnel lens is measured to test focusing quality of the lens.

This thesis aimed to develop a novel micro thermal electric generator (£g-TEG) with a series-array bridge microstructure utilizing microelectromechanical systems (MEMS) technology. By integrating the tens of thousands of micro-thermocouple in a centimeter square area, the temperature difference between the hot plane and cold plane of the presented £g-TEG can be converted into a useful electrical power. The thermoelectrically transferred output electrical power is suitable for recharging various mobile communication products. There are two main configurations of the conventional £g-TEGs have been proposed, including the vertical and lateral structure types. The heat flow of the vertical-type £g-TEG can be directly transferred by the thermocouples and hence the energy loss through the substrate can be efficiently reduced and the thermoelectrical conversion efficiency is usually higher than vertical-type £g-TEG. However, to obtain a useful electrical power output, the height of the vertical-type £g-TEG usually more than 100 micrometers and this will increase the production difficulty and fabrication cost. In contrast, the height of the lateral-type £g-TEG is only about several micrometers and hence the production difficulty and fabrication cost are lower than vertical-type £g-TEG. The non-neglect energy loss through the substrate of lateral-type £g-TEG will constrain the efficiency of electrical power generation. Using the surface micromachining technology, tens of thousands of suspending micro polysilicon thermocouple are integrated and serially connected to increase the efficiency of electrical power generation and reduce the substrate energy loss. The main fabrication processes adopted in this research are including seven thin-film deposition processes and five photolithography processes. The implemented Poly-Si based £g-TEG demonstrates a maximum temperature difference of 1.29¢J between the hot plane and cold plane (under nine different substrate temperatures), a maximum output voltage of 4.47 V/cm2 and a maximum output power of 601.4 nW/cm2. The comparison and analysis of experimental and simulation (ANSYS) results under the nine different substrate temperatures are investigated and the influence of length of suspending micro thermocouples is also discussed in this work.

This thesis presents fabrication of shunt, capacitive contact type RF MEMS switches which are designed according to given mm-wave performance specifications. The designed switches are modified for investigation in terms of reliability and lifetime. To observe the real-time performance of switches a time domain measurement setup is established and a CV (capacitance vs. voltage) curve measurement system is also included to measure CV curves, pull-in and hold-down voltages and the shifts of these due to actuations. By using the established setup reliability and lifetime measurements under different bias waveforms in different environments are performed. After investigation for the most suitable condition for improving lifetime long-term tests are performed and the outstanding result of more than 885 hours of operation under cycling bias waveform is obtained.

A reflective type Fresnel lens using an array of micromirrors is designed and fabricated using the MUMPs?? surface micromachining process. The focal length of the lens can be rapidly changed by controlling both the rotation and translation of electrostatically actuated micromirrors. The suspension spring, pedestal and electrodes are located under the mirror to maximize the optical efficiency. The micromirror translation and rotation are plotted versus the applied voltage. Relations are provided for the fill-factor and the numerical aperture as functions of the lens diameter, the mirror size, and the tolerances specified by the MUMPs?? design rules. Linnik interferometry is used to measure the translation, rotation, and flatness of a fabricated micromirror. The reflective type Fresnel lens is controlled by independent DC voltages of 16 channels with a 0 to 50V range, and translational and torsional stiffness are calibrated with measured data. The spot diameter of the point source by the fabricated and electrostatically controlled reflective type Fresnel lens is measured to test focusing quality of the lens.

For the application of 4G wireless communication system, this thesis aims to develop a high-quality-factor and low-power-dissipation suspending micro-inductor using electrochemical deposition and surface micromachining technologies. This research presents three technical points to improve the quality factor and reduce the power dissipation of micro inductor, including (i) to adopt a low resistivity material (copper) as the conducting layer to decrease the Eddy current due to the skin effect and reduce the total series resistance and energy loss, (ii) to utilize a suspending structure to diminish the power loss through the substrate and (iii) to replace the silicon wafer with a high resistance substrate (Corning 7740) to compress effectively the power dissipation in high frequency operation. The implemented suspending micro-inductors were characterized by a commercial network analyzer (Agilent E5071C) under 0.5~20 GHz testing frequency range. All the inductances and quality factors of the micro-inductors proposed in this thesis are extracted by the Agilent ADS software. The optimized value of the quality factor is around to 24.9 and the corresponding inductance is equal to 5.43 nH .

Utilizing the bulk and surface micromachining technologies, this thesis designed and fabricated a piezoresistive pressure microsensor for developing an in-vivo and real-time biomedical detection microsystem to monitor the uric pressure in patients¡¦ bladder. In this study, the main processing steps include the implantation of a moderate boron ion concentration into the N-epitaxial silicon layer to form the piezoresistors, anisotropic etching the backside silicon substrate to create a cavity by 30% KOH solution in 80¢XC temperature, and anodic bonding of the silicon based pressure microsensor and the hole-drilled glass sustain. To obtain the optimum design specification of the piezoresistive pressure microsensor, this study compared the characterization of the four types of devices with three different pressure sensing area (As) and two different length/width ratios (L/W) of the N-epitaxial piezoresistors. Based on the measurement results, the highest sensitivity (0.0076mV/(V*kgf/cm2) can be achieved as the As and the L/W ratio are equal to 1050 ¡Ñ 1050 £gm2 and 90/9 £gm/£gm, respectively. Such sensitivity is suitable for the application of bladder pressure detection microsystem. A very high sensing linearity (99.6%) can also be demonstrated in this research and this value approach to that of the commercial pressure sensor. On the other hand, through cooperation with another laboratory, this work has established a prototype of the uric pressure detecting microsystem by assembled with the piezoresistive pressure microsensor, a control ASIC and a radio-frequency (RF) module.

This thesis presents the design and fabrication of coplanar waveguide to microstrip transitions and planar spiral inductors, and the design of metal-insulator-metal capacitors, a planar band-pass, and a low-pass filter structures as an application for the inductors and capacitors using the RF MEMS technology. This thesis also includes a packaging method for RF MEMS devices with the use of benzocyclobutene as bonding material. The transition structures are formed by four different methods between coplanar waveguide end and microstrip end, and they are analyzed in 1-20 GHz. Very low loss transitions are obtained by maintaining constant characteristic impedance which is the same as the port impedance through the transition structures. The planar inductors are formed by square microstrip spirals on a glass substrate. Using the self-inductance propery of a conductive strip and the mutual inductance between two conductor strips in a proper arrangement, the inductance value of each structure is defined. Inductors from 0.7 nH up to 20 nH have been designed and fabricated. The metal-insulator-metal capacitors are formed by two coplanar waveguide structures. In the intersection, one end of a coplanar waveguide is placed on top of the end of the other coplanar waveguide with a dielectric layer in between. Using the theory of parallel plate capacitors, the capacitance of each structure is adjusted by the dimensions of the coplanar waveguides, which obviously adjust the area of intersection. Capacitors from 0.3 pF up to 9.8 pF have been designed. A low-pass filter and a band-pass filter are designed using the capacitors and inductors developed in this thesis. In addition to lumped elements, the interconnecting transmission lines, junctions and input-output lines are added to filter topologies. The RF MEMS packaging is realized on a coplanar waveguide structure which stands on a silicon wafer and encapsulated by a silicon wafer. The capping chip stands on the BCB outer ring which promotes adhesion and provides semi hermeticity. Keywords: Transition between transmission lines, planar spiral inductor, metal-insulator-metal capacitor, RF MEMS packaging, surface micromachining.